Thermal actuators



Sept. 7, 1965 a. SZEKELY THERMAL ACTUATORS Filed Feb. 25, 1963 FIGZ mm mm s we G R M O E G FIGS ATTORNEY- United States Patent 3,204,461 THERMAL ACTUATORS George Szekely, 3123 Bailey Ave., Bronx, New York, N.Y. Filed Feb. 25, 1963, Ser. No. 260,670 12 Claims. (Cl. 7335S) The present invention relates to thermal actuators to control the operation of various heating devices as for instance egg cookers, sausage cookers and the like and has general use in the control of heating processes. More particularly, these thermal actuators are of the type in which a heat-affected medium or member is made to move because of its expansion upon reaching a certain temperature and thereby otters motion to a means, as for example, the operating element of a switch, valve or trip to control the heat source or incident mechanism.

An object of this invention is to provide novel and improved thermal actuators of the character mentioned, which operate when the stufr being subjected to a heating process has had a prescribed caloric intake, after reaching a predetermined temperature.

Another object thereof is to provide novel and improved thermal actuators of the kind described, ofiering a timing facility having no moving parts and yet accomplishing a prescribed delaying action which may be of any desired duration.

A further object thereof is to provide that said timing can be adjusted to change the heat intake for the stuff being processed or otherwise subjected to the action of heat.

Still a further object of this invention is to provide thermal actuators of the character set forth, of novel and improved construction and mode of operation, which have the mentioned attributes, and which are simple in construction, reasonable in cost to manufacture and etficient in carrying out the purposes for which they are designed.

Other objects and advantages will become apparent as this disclosure proceeds.

For the practice of this invention, one form it may assume, comprises a structure including an outer casing of a material which is a non-conductor or a very poor conductor of heat. However, the substantial part, or all of one of the casings walls, is of a metal which is a very good heat conductor. Spaced from such wall inside the casing, is a heat-conductive container which holds,

for instance,.a wax and there is heat-insulative structure connecting said wall and wax-holding container to provide a confined air space therebetween. A spring-biased rod slidably fitted through another wall of said casing, is so associated, that upon the melting of the wax, such rod is shifted by the movement of the molten wax due to the expansion of the wax, which occurs when it passes from the solid into the liquid state. Rod movement is used to actuate a switch, valve or trip to control the heat source or its effect.

This device in use is set, for instance, within the water in an egg or sausage cooker, or is set in an oven chamber or other heat-receiving environment. The casings conductive wall acts as a heat antenna to bring heat from the stufr or environment being heated, through said confined air space and thence to the wax-holding container. It is evident that the delay of the passage of heat through said intermediate, confined air space, acts as a timer determining the heat intake of the stuff being processed or the environment being heated, before shut-off or other incident the actuator is arranged to control. Making said confined air space adjustable in volume, provides an adjustable timer.

A more detailed description will now be given of the several embodiments shown in the drawing which is part of this specification, and in which drawing, similar chartween said rod and the wax.

3,204,461 Patented Sept. 7, 1965 acters of reference indicate corresponding parts in all the views.

FIG. 1 is a central elevational section of a thermal actuator embodying teachings of this invention. Here, the confined air space is fixed.

FIG. 2 is a similar view of a modified construction in which the air space volume is adjustable.

FIG. 3 is a similar view of another modified construction.

In the drawing, the thermal actuator shown in FIG. 1, includes a casing designated generally by the numeral 15, comprised of an inverted receptacle 16 of a material which is a poor or a non-conductor of heat as Bakelite or compressed asbestors, for example; such receptacle being closed by a cap 17 made of copper or other metal which is a good heat conductor. Within this casing, is an upright bellows 18 which is closed by the discs 19, 20 and filled with a meltable wax 21, or a liquid or gas which'expands considerably when heated. Said disc 20 which is of copper or other good heat-conductive material, is secured atop a heat-insulative ring or tubular member 22 which may be of compressed asbestos or the like; said ring being secured to the conductive cap 17. It is evident that a confined air space of fixed volume is thus made to exist at 23. An upright rod 24 of low heatconductivity, may have a head 24' resting against the top of the bellows structure and is biased by a spring 25 to maintain such contact. This rod is slidably positioned through a proper sealing member 26 which is mounted in the upper wall of the casing 15, from which it extends outside the casing.

It is evident that upon suspending this actuator in a heated environment, as for instance within an oven chamber or the water for boiling in an egg or sausage cooker, said cap 17 as a heat antenna will conduct heat to the air chamber 23 and from there the heat would pass slowly to the contents of the bellows 18, which will expand upon the increase of its temperature and cause the rod 24 to rise. This rod movement is utilized to cause shift of an operating element 27 of a switch, valve, trip or the like in manner well knownto cut ofi the heat source or otherwise control same, or to operate a signal or other indicator.

The thermal actuator shown in FIG. 2 includes a cas an inverted receptacle 29 of Bakelite, asbestos or the like,

closed by a resilient diaphragm 30 which is of non-heatconductive material; said diaphragm being held in place by a ferrule 31 whose inward flange 31 is relatively narrow. Suspended upright within this casing 28, on support element 32, 33 of heat-insulative material, is a bottleshaped container 34 made of copper, which is filled up to a bit into its neck 34', with a meltable wax 35. The lower end of a rod 36 fits slidingly within said neck and there is a packing element 37 which is slidably fitted be- Said rod 36 is biased downwardly by a spring 38 and is slidably fitted through a sealing member 39 mounted in the upper wall of the easing 28, outwardly of which, said rod extends.

The wax-holding bottle or container 34 extends downwardly as a fixed piston within the cylinder 40, only whose bottom 41 is heat-conductive. Such bottom member may be a headed plug screw position-ed through the center of the diaphragm 30 and in threaded engagement with the heat conductive block 42 which is against the exposed face of the diaphragm, exterior the casing 28. The cylindrical wall 43 of the cylinder 40 is of heat insulative material, spaced from the diaphragm. The parts 41 and 42 are preferably of copper and act as the heat antenna; the annular channel 42' offering increased heat-receiving surface. Said container 34 is spaced from the bottom 41 of said cylinder 40, thereby creating the air chamber 48 whose volume can be changed by manipulation of the adjustment screw 44 which is in threaded engagement with the frame element 45 and swivelled at 46- to the antenna block 42. Said screw has a stop pin 44' to limit downward movement. I

It is evident that upon suspending this thermal actuator in a heated environment, the antenna comprising the members 41, 42 which are in aggregate the heat-conductive portion of a wall of the casing 28, will bring heat to the air chamber 48 and from there the heat would be conducted slowly to the wax 35, which upon melting, will expand and rise, thereby shifting the rod 36 upward to work the operating element 27' of a switch, valve or the like, for the purposes hereinbefore set forth.

A further embodiment of a thermal actuator following the teachings of this invention, is shown in FIG. 3, wherein the receptacle 47, its copper closing cap 48 which serves as the heat antenna and the spring-biased rod 49 are all of the same character and associated in like manner as occur-s in the other embodiments herein illustrated. Interior the casing 50, a heat-insulative tubular member 51 is secured in upright position to the cap 48' and covered so it is closed by a metal disc 52, to form a confined air chamber. However, it is to be noted that in this embodiment, the effective air space acting as the timing means is indicated at 53, which exists within said tubular member 51, between the metal piston-like member 54 and the disc 52; said piston being secured to the end of a metal screw 55 which is threadedly engaged in a metal nut member 56 which is fixed through the cap 48' and provided with an O-ring 57 to serve as a packing seal as shown. Said screw 55 has a head 58 at its exposed end for adjusting the position of the piston member 54 in its cylinder '51, and thus vary the volume of the air space 53. The bi-metal thermostatic elements 59, 60 are secured in spaced relation atop the conductive disc 52; such elements being cantilevers in crossing relation which bear against the head 61 on the lower end of the rod 49; such elements 59, 60 being adapted to swing in an upward direction respectively, upon reaching a certain temperature, thereby causing said rod 49 to be shifted upward for employment as indicated for the actuators of FIGS. 1 and 2. The mode of use and operation of this actuator of FIG. 3, is evident without further explanation.

=If timing is relied on by a fixed air chamber as 23 in FIG. 1, or if further adjustment of timing is desired with the variable air chamber as shown in the actuators in FIG. 2 or 3, the action of the influence of the heat source may be terminated sooner and be adjustable, if the act-uator is fitted with an adjustable trip 62 for the element 27, whereof 63 denotes a threaded socket at the upper end of the rod 24 which is made to shift, and the numeral 64 indicates the threaded portion at the bottom of an accessible adjustment rod 65, to vary the distance A. It is evident that the shorter this distance is made, the sooner will the element 27 be moved.

If an actuator taught herein is to be used to operate a switch, such switch structure may be housed in the outer casing and offer connection terminals on the casings exterior. In such instances, the slidable rod may even be dispensed with in the embodiment'of FIG. 3, or be wholly within such casing in the embodiments shown in FIGS. 1 and 2, all of which is readily understandable without further illustration.

Actuators as shown herein may be cart-ridges adapted to be releasably set in suitable sockets or adapters, not shown, in egg or sausage cookers and oven chambers or the like. For appliances as egg cookers for instance, it would be practical to have three thermal actuators of different timing character, in order to be installed as needed to cook soft, medium and hard boiled operations respectively. These actuators, of course, need be initially cold when installed to control a heating operation.

Dimensions of the parts, the melting temperature of the wax used at 21 and 35, which may be beeswax, the physical behaviors of other expandable media, as for instance, naphthalene which may be used in the sealed bel lows 18, and the specifications of the thermostatic bars 59, 60, are chosen so that the thermal actuator resulting, shall function properly in its destined sphere of operation, so that there occurs a predetermined thermal intake in the substance or in the environment being subjected to the heat source, at which time such actuator shall operate to cut-off or otherwise control the heat source, or operate a switch means to close a signal circuit, depending upon the nature of the installation.

This invention is capable of numerous forms and various applications without departing from the essential features herein disclosed. It is therefore intended and desired that the embodiments shown herein shall be deemed merely illustrative and not restrictive and that the patent shall cover all patentable novelty herein set .forth; reference being had to the following claims rather than to the specific description herein to indicate the scope of this invention.

I claim:

1. In a thermal actuator of the character described, adapted to be placed in an environment receiving heat, a casing of heat-resistive material having a wall which has a first structure of relatively high heat-conductive quality exposed outside said casing and extending into said casing, a member of relatively high heat-conductive quality within said casing, spaced from said first structure, a second structure of relatively low heat-conductive quality positioned inside the space between and contacting opposite surfaces respectively of said first structure and member; said second structure constituting the only path for heat to travel from the first structure to said member, and a means carried by said member, having the character that a movement thereof will occur when heated to a predetermined temperature.

2. A thermal actuator as defined in claim 1, wherein said means includes a medium which expands appreciably when heated to said predetermined temperature; such expansion constituting the mentioned movement.

3. A thermal actuator as defined in claim 1, wherein said means includes an element which bends appreciably when heated to said predetermined temperature; such bending constituting the mentioned movement.

4. A thermal actuator as defined in claim 1, including means to change the distance between the first structure and said member; the second structure being of the character to allow such change.

5. A thermal actuator as defined in claim 4, wherein said distance-changing means is accessible outside the casing for manipulation.

6. A thermal actuator as defined in claim 1, wherein said second structure includes a space afforded by a tubular member of heat-resistive material, forming a chamber within the casing, with said member and first structure.

7. A thermal actuator as defined in claim 6, wherein the casing comprises a receptacle, closed by said Wall; said wall constituting said first structure.

3. A thermal actuator as defined in claim 6, wherein said first structure is movable through said wall and includes a piston movably fitted in said tubular member for movement towards and away from said heat-conductive member, whereby the volume of said chamber is adjustable.

9. A thermal actuator as defined in claim 6, wherein said wall is a resilient diaphragm carrying said tubular member and the first structure; the heat-conductive member including a piston movably mounted in said tubular member; said actuator including means carried outside the casing, adapted to move said diaphragm whereby the first structure will move towards and away from said piston; said heat-conductive member having said piston, being fixed in said casing.

10. A thermal actuator as defined in claim 1, wherein the heat-conductive member is an upright bottle-form and the mentioned means is a medium which expands appreciably when heated to said predetermined temperature; said medium being within said bottle-form, and including an element :slidably mounted in the neck of said bottle-form, adapted to be lifted upon the expansion of said medium.

11. A thermal actuator as defined in claim 1, wherein the heat-conductive member is a bellows and the mentioned means is a medium which expands appreciably when heated to said predetermined temperature; said medium being within said bellows and said bellows being adapted to expand upon the expansion of said medium.

12. A thermal actuator as defined in claim 1, wherein the mentioned means is a bi-metal thermostatic element adapted to bendably change its form when heated to said predetermined temperature.

References Cited by the Examiner UNITED STATES PATENTS ISAAC LISANN, Primary Examiner.

ROBERT L. EVANS, Examiner. 

1. IN ATHERMAL ACTUATOR OF THE CHARACTER DESCRIBED, ADAPTED TO BE PLACED IN AN ENVIRONMENT RECEIVING HEAT, A CASING OF HEAT-RESISTIVE MATERIAL HAVING A WALL WHICH HAS A FIRST STRUCTURE OF RELATIVELY HIGH HEAT-CONDUTIVE QUALITY EXPOSED OUTSIDE SAID CASING AND EXTENDING INTO SAID CSING, A MEMBER OF RELATIVELY HIGH HEAT-CONDUCTIVE QUALITY WITHIN SAID CASING, SPACED FROM SAID FIRST STRUCTURE, A SECOND STRUCTURE OF RELATIVELY LOW HEAT-CONDUCTIVE QUALITY POSITIONED INSIDE THE SPACE BETWEEN AND CONTACTING OPPOSITE SURFACES RESPECTIVELY OF SAID FIRST STRUCTURE AND MEMBER; SAID SECOND STRUCTURE CONSTITUTING THE ONLY PATH FOR HEAT TO TRAVEL FROM THE FIRST STRUCTURE TO SAID MEMBER, AND A MEANS CARRIED BY SAID MEMBER, HAVING THE CHARACTER THAT A MOVEMENT THEREOF WILL OCCUR WHEN HEATED TO A PREDETERMINED TEMPERATURE. 